SAO Progessive is an in-depth (and somewhat altered) telling of Aincrad. It tells the story of what happens to Kirito on the lower levels, and how he evolves into the bad-ass that he already is when the main story begins.

Mother's Rosario, Caliber, and Girls Ops are all side stories set between the Phantom Bullet and Alicization arcs.

Also, in case you were curious, the SAO video games take place after the Aincrad plot, but inside the original SAO game--essentially rewriting the universe starting from the ending of LN volume 1 (or episode 14 of the anime).

SAO Progessive is an in-depth (and somewhat altered) telling of Aincrad. It tells the story of what happens to Kirito on the lower levels, and how he evolves into the bad-ass that he already is when the main story begins.

Mother's Rosario, Caliber, and Girls Ops are all side stories set between the Phantom Bullet and Alicization arcs.

Also, in case you were curious, the SAO video games take place after the Aincrad plot, but inside the original SAO game--essentially rewriting the universe starting from the ending of LN volume 1 (or episode 14 of the anime).

I don't care for video games of any kind so I'll give them a miss, but I'll try and collect the manga in order.